West Antarctica is well known for its rapid and strong reaction to environmental change. Since the beginning of the recent warming trend in the 1980ies the West Antarctic Peninsula belongs to the fastest warming regions on Earth. In places temperatures increased by 2.5°K over 50 years (Faraday/Vernadsky Station) thus leading to decreasing sea-ice formation and increasing glacier retreat. Situated in the sensitive latitudes between 62 and 63°S, Maxwell Bay and its tributary fjord Potter Cove are the focus of the international interdisciplinary research project IMCOAST. Here we present results of the sedimentology working group that is investigating modern and subrecent sedimentary processes in order to emphasize the climate signal in the sedimentary record. Five age-dated sediment cores (lengths between 126 and 980cm) from locations in Maxwell Bay, about 130 seafloor samples on a 200m grid in Potter Cove, shallow (high-resolution) seismic transects measured in Potter Cove and Maxwell Bay as well as areawide sidescan sonar images and single-beam bathymetric data from Potter Cove form the data base for the interpretations. Shallow seismics reveal more than 50m well-layered sediments within Maxwell Bay, but very low sound penetration in Potter cove at water depths < 200 m. The inner Potter Cove at water depths of < 60m shows strong traces of ploughing icebergs. These are most likely also responsible for the lack of sound penetration in the outer cove where large icebergs likely mixed up and compacted sediment in many places. Sediment core PS69/335 (980cm long, spanning the past 1700 years) taken between Potter and Marian coves (Maxwell Bay) reveals generally coarser grained sediments during colder climate phases such as the Little Ice Age (AD 1350-1900) and finer sediments during warm phases such as the Medieval Warm Period (AD 900-1350). This is interpreted to be a result of increased discharge of meltwater carrying fine-grained sediment during warmer phases and, contrary, reduced supply of finer sediment during the cooler phases. Some of the sediment cores mirror this process, others show only weak signals of this kind, hence, suggesting pathways for suspension-laden meltwater within Maxwell Bay. The recent climatic conditions would be apt to produce a meltwater-signal environment which we investigated in-situ in Potter Cove. However, although we witnessed a number of meltwater plumes within Potter Cove during the field campaign in 2010, sediment carrying the 'warm-phase' signal (mainly sediment with a grain-size mode at 16 µm) was found only sparsely distributed in Potter Cove. We conclude that either the routing of the meltwater plumes is different today when compared to earlier warm phases, or (more likely) this is the result of the tidewater glacier (Fourcade Glacier) at the head of Potter Cove, that has dramatically retreated through the past decades and became land-based only few years ago. It can be speculated that the glacier, once it retreated back on land, largely stopped movement. As a result the production and discharge of fine-grained material decreased which could explain the lack of this material in the area.
AWI Organizations > Biosciences > Coastal Ecology
Helmholtz Research Programs > PACES I (2009-2013) > TOPIC 2: Coastal Change > WP 2.3: Coastal Systems under Global and Regional Pressures